Tuesday, March 27, 2012

Reading Comprehension: Most Supported by Passage

This is another post in our series describing the classification system Zen of 180 uses for the reading comprehension section. If you're not sure how to approach studying for the LSAT, our 19 reading comprehension standards break it down into manageable chunks; also, our free online LSAT analyzer will let you know which types of passage structures give you the most trouble.

Today's task, most supported by passage, requires an examinee to combine explicit information in the passage, often highlighted in the question stem, and choose a factual statement or conclusion that can be drawn from them. It is analogous to the most strongly supported by [stimulus] logical reasoning task, and similarly benefits from cleanly prestating the topic's actors, relationships, and degrees of certainty for each.

This NASA video is full of many layers of nested extrapolations. Based on what we know, how would our solar system look from another system, from millions of years ago, and can scientists find planets using this technique?
Because of the need to prephrase the actors, relationships, and degrees of certainty, marking the passage's structural signposts that clearly assign examples and counterexamples to their actors will help to quickly eliminate distractors. You can read through our discussion of main idea or title and primary purpose to review these highlighting techniques.

The question stems for most supported by passage questions are often difficult to spot, as they are easily conflated with passage or author implies. At its base, the difference between the two tasks is between extrapolating facts and identifying opinion; today we're working on making a clean logical inference from explicit scientific evidence, which is why the sample question we'll be using from LSAC's website is classified as a most supported by passage and is not an opinion standard.

Some examples of most supported by passage question stems from modern LSATs:
Based on the passage, which one of the following is most likely to be true of any [category] used to replace [subcategory] in the process mentioned in the first paragraph?

Which one of the following is most strongly implied by
the passage? 
It can be inferred from the passage that if the [actor] mentioned in lines 46–47 were eliminated . . . which one of the following would be the most likely to occur?
The passage most strongly suggests which one of the following about the use of [subject]?
We'll be using the same passage we introduced in the passage or author says explanation, a comparative passage where two authors in the 1990s discuss anthropomorphic climate change.
       Passage A
            In January 1995 a vast section of ice broke off the
       Larsen ice shelf in Antarctica. While this occurrence,
       the direct result of a regional warming trend that began
       in the 1940s, may be the most spectacular
(5)   manifestation yet of serious climate changes
       occurring on the planet as a consequence of
       atmospheric heating, other symptomsmore intense
       storms, prolonged droughts, extended heat waves, and
       record flooding—have been emerging around the
(10) world for several years.
            According to scientific estimates, furthermore,
       sea-level rise resulting from global warming will
       reach 3 feet (1 meter) within the next century. Such a
       rise could submerge vast coastal areas, with
(15) potentially irreversible consequences. 
            Late in 1995 the Intergovernmental Panel on
       Climate Change (IPCC) reported that it had detected
       the “fingerprint“ of human activity as a contributor to
       the warming of the earth’s atmosphere. Furthermore,
(20) panel scientists attributed such warming directly to
       the increasing quantities of carbon dioxide released
       by our burning of fossil fuels. The IPCC report thus
       clearly identifies a pattern of climatic response to
       human activities in the climatological record, thereby
(25) establishing without doubt that global warming can
       no longer be attributed solely to natural climate        
       variability.
This passage introduces the topic of global warming and the IPCC's findings that humans are contributing to the phenomenon. From these findings, the author jumps to their clearly stated opinion on the topic (pink highlights), which conclude the final paragraph.
       Passage B
            Over the past two decades, an extreme view of
       global warming has developed. While it contains
(30) some facts, this view also contains exaggerations and
       misstatements, and has sometimes resulted in
       unreasonable environmental policies.
            According to this view, global warming will cause the
       polar ice to melt, raising global sea levels,
(35) flooding entire regions, destroying crops, and
       displacing millions of people. However, there is still a
       great deal of uncertainty regarding a potential rise in
       sea levels. Certainly, if the earth warms, sea levels
       will rise as the water heats up and expands. If the
(40) polar ice caps melt, more water will be added to the
       oceans, raising sea levels even further. There is some
       evidence that melting has occurred; however, there is
       also evidence that the Antarctic ice sheets are
       growing. In fact, it is possible that a warmer sea-
(45) surface temperature will cause more water to
       evaporate, and when wind carries the moisture-laden
       air over the land, it will precipitate out as snow,
       causing the ice sheets to grow. Certainly, we need to
       have better knowledge about the hydrological cycle
(50) before predicting dire consequences as a result of
       recent increases in global temperatures.
            This view also exaggerates the impact that human
       activity has on the planet. While human activity may
       be a factor in global warming, natural events appear
(55) to be far more important. The 1991 eruption of Mount
       Pinatubo in the Philippines, for example, caused a
       decrease in the average global temperature, while El
       Niño, a periodic perturbation in the ocean’s
       temperature and circulation, causes extreme global
(60) climatic events, including droughts and major
       flooding. Of even greater importance to the earth’s
       climate are variations in the sun’s radiation and in the
       earth’s orbit. Climate variability has always existed and
       will continue to do so, regardless of human
(65) intervention.
This second passage clearly tries to downplay the evidence introduced in Passage A, as well as present several countervailing factors and natural examples that outweigh humanity's impact on global warming. The signposts for each point of view (pink), the examples and counterexamples each author uses (blues and cyans, respectively), as well as the more structural elements (green and red), will help us find and reference back for any passage or author says questions. 
The author of passage B would be most likely to make which
one of the following criticisms about the predictions cited in
passage A concerning a rise in sea level?
This question stem is one of the most complicated for this task, as it exemplifies the difficulty of classifying the task as either identifying Passage B author's opinion on Passage A or extrapolating from the evidence that the author includes in Passage B's argument. Ultimately, though, you'll still want to pay attention to the actors, relationships, and degrees of certainty for either task. If an answer choice correctly maps on to the relevant portion(s) of the passage, then it will be correct.

In this case, the author of Passage B clearly thinks that the anthropomorphic global warming opinion in Passage A is "exaggerated" and based on evidence that we don't fully understand and that is, in the author's opinion, outweighed by other, naturalistic, causes. Ideally, you would have already answered a main idea or primary purpose question prior to reaching today's question, as reframing to that prephrase would make comparing the answer choices much easier.
(A) These predictions incorrectly posit a causal
      relationship between the warming of the earth
      and rising sea levels.
(B) These predictions are supported only by inconclusive
      evidence that some melting of the polar ice caps
      has occurred.
(C) These predictions exaggerate the degree to which
      global temperatures have increased in recent
      decades.
(D) These predictions rely on an inadequate
      understanding of the hydrological cycle.
(E) These predictions assume a continuing increase in
      global temperatures that may not occur.
Answer choice D is a factual statement that is supported by lines 48-52, and not an opinion, because it merely points out that scientists do not currently fully understand how the hydrological cycle will react to the admittedly observed global warming phenomenon. "Rely" does not convey the evaluative element necessary to convey the author's opinion, as it points out a gap in scientists' current abilities to properly extrapolate from the underlying evidence. This answer choice fits nicely in with our prephrase of Passage B's actors, relationships, and degrees of certainty: we shouldn't make predictions of global ruin until we better understand the mechanisms underlying the phenomenon.

Answer choice A ignores lines 38-39, where the author admits that warming has some relationship to sea levels; stating that the relationship is more complicated than it is treated in Passage A is not denying causality.

Answer choice B inappropriately limits the author to criticizing Passage A on the evidence of melting ice caps. Line 30 uses plural "facts," and the rest of the argument focuses on rising sea levels, of which polar ice caps are only a piece.

Answer choice C imputes information for Passage B's author that neither passage discusses: we only know that temperatures have risen, not by how much.

Answer choice E similarly would require evidence that neither passage presents. Although both passages discuss future effects of global warming, neither rely on a continuing increase.